AVENTURINE  GLAZES 


BY 


JOHN  SHERMAN  LATHROP 


THESIS 


FOR  THE 


DEGREE  OF  BACHELOR  OF  SCIENCE 

IN 

CERAMIC  ENGINEERING 


COLLEGE  OF  ENGINEERING 
UNIVERSITY  OF  ILLINOIS 


1922 


•-Mil 


Digitized  by  the  Internet  Archive 
in  2015 


https://archive.org/detaiis/aventurineglazesOOIath 


INDEX 


Page 

I  Introduction  . . • . o 1-5 

II  Work  Conducted  by  Previous  Experimenters  6-7 

A,  Work  done  by  U.S. Bureau  of  Mines 6 

B.  Work  done  by  Nathan  Bromberg 6-2> 

III  Scope  of  Present  Investigation  S 

IV  Method  of  Investigation S-9 

V Burning  9 

VI  Method  of  Preparing  Glazes  10 

VII  Materials  Used 11 

VIII  Trial  Pieces 11 

IX  Effect  of  Variations  in  Al20^,  FegO^.  . . • 11-2S 

Ao  First  Series 11-20 

B.  Second  Series 21=-24- 

C.  Third  Series 24-27 

D.  General  Conclusions  from  First  Part 27-28 

X  Effect  of  Variations  in  Na20,  K2O,  CaO  and  PbO  . . . 2S-3^ 

A,  Conclusions  from  Second  Part 28-3^ 

XI  General  Conclusions  drawn  from  Experiments  on 

Aventurine  Glazes  34-35 


INDEX  TO  FIGURES 

Page 

Fig,  I Time -temperature  Curve  for  Aventurine 

glazes  Maturing  at  Cone  1 l4a 

Fig. II  Area  of  Investigations  of  Variable  Con- 

stituents of  the  Aventurine  Glazes 
of  Part  1 12a 

Fig. Ill  Chart  showing  location  of  all  Glazes  on 
Tri-axial  chart  together  with  Dia- 
gramatic  Presentation  of  Results  ....  12b 

Fig,  IV  Time-temperature  Curve  for  Aventurine 

Glazes  burned  at  cone  3 24a 

Fig,  V,VI,VII,VIII,IX  Presentation  of  the  R 0 
components  of  each  glaze  together 
with  the  location  of  each  glaze 
on  Tri-axial  diagrams  for  glazes 
varying  in  the  R 0 components 29a-29e 


STUDIES  IN  AVENTURINE  GLAZES, 

I 

Introduction 

Of  all  the  types  of  glaaes,  probably  the  most  beautiful  and 
yet  the  most  difficult  to  produce  are  the  crystalline  glazes. 

There  has  been  very  little  technical  research  done  on  this  subject 
and  undoubtedly  if  more  work  were  done  on  the  subject  and  more  in- 
formation  were  available,  crystalline  glaaes  could  be  produced  and 
controlled  as  easily  as  other  glazes.  The  glaze  composition,  the 
heat  treatment  of  the  glaze,  and  the  body  composition,  are  factors 
which  have  to  be  studied  for  each  particular  glaze. 

There  are  two  typos  of  crystalline  glazes^;-  The  first  type, 
the  macro-crystalline  glazes,  includes  the  aventurine  glaze,  some- 
times called  "goldstone"  or  "tiger  eye".  In  this  type  the  crystals 
separate  out  of  the  molten  matrix  on  cooling  of  a size  readily  vis- 
ible to  the  maked  eye.  The  second  type,  the  micro-crystalline 
glazes,  includes  some  of  the  mott  glazes.  In  this  type,  the  entire 
mass  crystallizes.  For  developing  aventurine  glazes,  Stull  recom- 
mends applying  metallic  oxides  to  the  body  and  covering  this  with 
a boric  acid  glaze.  When  the  glaze  fuses  and  becomes  fluid,  it 
takes  part  of  the  metallic  oxide  into  solution  and,  if  enough  of 
it  is  dissolved,  the  glaze  becomes  supersaturated  and  crystals  se- 
parate out  on  cooling, 

p 

Mellor^  has  given  a good  explanation  of  the  formation  of 
cyrstalline  glazes  by  comparing  the  molten  matrix  with  ordinary 

^ R,  To  Stull  "Notes  on  the  Production  of  Crystalline  Glazes". 

Trans,  Am.  Cer,  Soc,  Vol.  VII,  190^  p,lS6 

J , W.  Mellor  "Crystallization  in  Pottery". 

Trans.  Eng,  Cer.  Soc.  Vol.  IV,  1902  p.52 


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solutions  as  follows:  "The  molecules  of  the  solution  resist  crys- 
tallization and  some  crystallizing  force  is  required  to  start  crys- 
tallization." 0stwald3  states  that  it  is  only  necessary  to  have 
one  millionth  part  of  a milligram  in  a solution  of  sodium  chloride  j 
to  overcome  the  passive  resistance  of  the  molecules  and  start  crys- 
tallization of  the  sodium  chloride.  Stull^  , in  comparing  the 
crystallizing  tendencies  of  various  oxides  draws  the  following  con- 
clusions! - 

I.  The  strongest  crystallizing  tendencies  are  given  to 
glazes  by  those  chemical  elements  of  low  atomic  weight  whose 
oxides  go  to  make  up  the  R 0,  such  as  sodium,  potassium,  mag- 
nesium, calcium,  manganese,  iron  zinc,  etc. 

II.  Those  metals  of  high  atomic  weight,  such  as  barium, 
lead,  etc.,  seem  to  impart  a glossy  nature  to  silicates  when 
used  in  sufficient  quantities,  which  is  unfavorable  to  crys- 
tallization. 

III.  Those  chemical  elements  of  higher  atomic  weight  whose  I 
oxides  make  the  acid  portion  of  a glaze  such  as  silicon,  titan-J 
ium,  phosphorus,  etc.,  produce  the  best  crystallizing  agents, 
while  those  of  lower  atomic  weight,  as  for  example,  boron, 
having  an  atomic  weight  of  11,  impart  a fluidity  and  brilli- 
ancy to  a glaze  which  is  detrimental  to  crystallization. 

IV.  The  introduction  of  an  R20^materially  assists  crystalli- 
zation in  some  cases,  while  in  others  it  is  detrimental  to  it, 

3 Zeit.  Phys.  Cehm.  1S97,  22,  2S9. 

Ibid  1.  Vol.  VI.,  p.  Igg. 


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^The  name  "Aventurine"  as  applied  to  glazes,  originated  from 
its  similarity  to  certain  types  of  quartz  and  feldspar  spangled 
with  scales  of  mica,  hematite  or  gothite,  They  give  off  fire-like 
reflections  when  held  in  a bright  light  and  are  known  as  aventurine  | 
feldspar  and  aventurine  quartz.  ! 

i 

Wohler6  produced  glazes  having  a similar  appearance  in  lS^9o  | 
Wartha?  obtained  an  aventurine  effect  by  first  applying  an  engobe  o 
iron  or  uranium  oxide  and  then  covering  the  same  with  a borax 
glaze . 

Aventurine  gla.zes  are  produced  by  mixtures  in  which  there  is 
an  excess  of  metallic  oxides  which  go  into  solution.  The  glaze 
matrix  becomes  saturated  with  the  metallic  oxide,  and  on  cooling, 
the  solvent  capacity  of  the  glaze  reaches  a maximum,  the  glaze  be- 
comes supersaturated,  and  the  excess  gradually  separates  out  in 
thin,  plate-like  crystals.  The  metallic  oxides  generally  used  in 
aventurine  glazes  are  those  of  iron,  chromium,  and  sometimes  copper 

C6 

Mellor*^  states  that  aventurine  glazes  are  more  easily  obtained  on 
red  tile  than  on  white  tile.  This  is  probably  due  to  the  fact  that 
the  glaze  dissolves  some  iron  oxide  from  the  body  and  aids  in  satur 
ating  the  glaze.  Stull^  advises  the  use  of  vitrified  bodies  which 
have  been  biscuited  at  a temperature  of  two  or  three  cones  higher 
than  that  of  the  glaze. 

Zimmerl^states  that  it  is  necessary  to  have;  IM^.^  a continu- 
ously oxidizing  fire;  2^^,  a gradually  increasing  temperature; 

^ H.  G.  Schurecht  — Journal  Amer.  Cer.  Soc.,  Vol.  3#  No.  12 

6 Thomind,  Ztg.,  1^96,  p.  219-  December,  1920. 

7 Ibid,  1^90  p.  170. 

^ Zeit.  Phys.  Chem.  1S97,  22,  2S9. 

9 Ibid  1, 

W.  H.  Zimmer.  ^^Crystallized  Odagea".  Trans  .Am. Cer  .Soc  «Vol  .14-1912  .| 


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3^  , a gradually  decreasing  tempeirature;  and  exclusion  of 

Al20^  from  the  glaze#  The  rates  of  crystallization  of  the  differ- 
ent glazes  vary  so  much  with  the  tempera^ture  that  the  rate  of  cool- 
ing after  burning  must  be  regulated  to  suit  the  glaze.  Correct 
cooling  is  of  as  much  importance  as  is  correct  composition.  The 
purpose  of  the  slowly  cooling  fire  is  to  give  the  crystals  time 
to  grow. 

Most  writers  are  of  the  opinion  that  the  "aventurine  effect" 
is  best  produced  by  introducing  iron  in  a suitable  form  into  a 
properly  constituted  glaze.  Mackler  determined  the  effect  of 
increasing  the  iron  oxide  content  in  glaz«s  of  the  cone  09  type 
and  found  that  when  35  parts  of  iron  oxide  were  added  to  100  parts 
of  glaze,  he  obtained  an  aventurine  effect,  but  the  color  of  the 
glaze  was  too  dark,  due  to  the  reduct ioh  of  the  iron  oxide  to  the 
ferrous  condition.  He,  therefore,  tried  20  per  cent  of  finely 
ground  metallic  iron  and  obtained  a transparent  yellow  glaze  with 
many  gold-like  crystals.  The  glaze  used  by  him  corresponded  to  the 
following  formulas- 

0.25  KoO  ) 

) 2.25  SiOp 

0.25  Na  0 ) 

2 ) 0.75  BgO, 

0.50  CaO  ) 

PatrikjlB  produced  artificial  crystals  of  hematite  by  melting 
a mixture  of  iron  sulphate  and  sodiuun  chloride  and  dissolving  in 
water.  Crystals  1 to  2 mm.  in  diameter  were  produced  in  this 
manner.  These  cyrstals  are  not  easily  dissolved  in  the  glaze  melt 

Thonind,  Zeitg.,  IS96,  p.  219. 

Ibid  11,  1S^6,  p.  275. 


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and  when  introduced  into 

a glaze  appear  as  bright  scales 

similar 

to  aventurine  glaaes. 

The  following  are  two  formulae 

for  aventurine  glazes 

8Ub“ 

mitted  by  Parmelee^^  and  reported  as  giving  good  golstone 

glazes:- 

Cone  2 glaze 

Fritt  for  cone 

2 glaze 

0.10  K«0 
2 

0.2  KpO  ] 

0,15  NapO! 

f 

0.3  NapOJ 

0o22  A1  0 

d ' 

0,2  AlnO-i) 

0.25  I 

2 3 

) 2.30  SiOp 

0,2  CaO 

)2.0  SiOp 

0 .30  BpO-z 

' 

' 0.6  BpO-z 

) 

0.35  PbO  ) '' 

0,15  FeO  ) 

0.2  PbO  ; 

0.1  FeO 

1 

Batch  Weights 

Batch  weights  for  fritt 

Fritt 

14-1 

Feldspar 

111 

Whiting 

Borax 

115 

White  load 

65 

Whiting 

20 

China  clay 

31 

White  lead 

52 

Flint 

64 

Flint 

4S 

Red  iron 

oxide 

6 

Red  Iron 

oxide 

S 

Cone  09  glaze 

Fritt 

for  Cone  09 

glaze 

0.40  NagO) 

0.5  NapO) 

) 0.4  BpO,) 
0.4  PbO  ) ^ 

2,0  SiOg 

) 0.03  AlpO,) 
0.46  PbO  ) 

2.1  SiOp 

0.14  FeO  ; 

0.32  BpO^  ) 

d 

Batch  Weights 

Batch  weights  for  fritt 

Fritt 

220 

Borax 

76 

Red  lead 

32 

Sodium  carbonate 

32 

Red  iron 

oxide 

5 

Red  lead 

91 

Ball  clay 

S 

Red  iron 

oxide 

S 

Flint 

24- 

Flint 

120 

• 13 

Professor  C.  W.  Parmelee,  Cer . 

Dept .,  University  of  Illinois. 

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II 

Discussion  of  Previous  Investigations. 

l^In  experiments  conducted  by  the  Bureau  of  Mines,  the  effect 

of  varying  iron  oxide  and  silica  was  studied  between  the  following 

limits  in  a cone  4 aventurine  glaze:  j 

0.05  AlpO,  ) 

0,4-  Na«0  ) ^ i 

^ ) 0.25  BpO^z  I 2A  » 4,2  SiO„ 

0.6  PbO  ) ^ ^ 

0.12-0. SI  Fc203) 

A,  Summary  of  Work  done  by  the  U.S. Bureau  of  Mines 

1.  Within  the  foregoing  experimental  limits  aventurine  glazes 
were  obtained  with  more  than  0.4-1  Fc20j  in  glazes  containing 

2.4-  Si02#  and  with  more  than  0.5S  Feg  0^  in  glazes  containing  4-. 2 
Si02  a 

2,  Glazes  with  0.4-1  to  0*73  FepO^  vary  in  color  from  red  to 
black  according  to  kiln  conditions,  red  being  produced  under  oxi- 
dizing conditions  and  black  under  reducing  conditions. 

3*  With  reducing  conditions  the  glazes  high  in  iron  become  a 
dull  black  with  a metallic  lustre.  By  applying  a thin  coating  of 
accone  02  lead  glaze  on  the  surface  of  such  a glaze  and  firing  in  an 
oxidizing  atmosphere,  a maroon  effect  is  obtained. 

4-.  Increasing  the  iron  content  increases  the  size  and  mmiber 
of  crystals  and  also  the  refractoriness  of  the  glazes. 

B.  Work  done  by  Nathan  Bromberg  on  Thesis  for  B.S. Degree 
in  Ceramic  Engineering,  University  of  Illinois,  1915* 

The  purpose  of  this  study  was  to  develop  aventurine  glazes 
which  would  mature  at  cone  010  (950°  C) , cone  1 (1150°  C)  and 
cone  5 (1230*^  C).  The  field  to  be  investigated  was  determined  on, 

iT — — - 

Ibid  5. 


[i 


f 


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. irv 

* » : : 


and  a rectangular  diagram  drawn  so  as  to  include  all  the  variations 
desired. 

Bromberg’s  General  Conclusions. 

From  the  results  of  the  foregoing  studies,  the  following  con-  | 

! 

elusions  may  be  drawn:  5 

1.  The  formation  of  crystals  depends  upon  the  slow  cooling 
of  the  glaze.  As  each  glaze  has  a different  rate  of  crystal- 
lization at  each  temperature,  the  cooling  curve  for  each  glaze 
should  be  determined  individually* 

2.  The  amount  of  Fe^O^  necessary  for  the  formation  of  aven- 
turine  crystals  depends  upon  the  glaze  and  may  vary  from  0.25 
to  0.6  molecules. 

3.  Increasing  the  Na^O  content  increases  crystallization. 

4.  Aventurine  crystals  may  be  formed  in  the  presence  of  .2 
molecules  of  A1_0^. 

5.  Aventurine  crystals  may  be  formed  in  the  presence  of 
CaO  even  when  there  is  as  much  as  0.4  molecule  present, 

6*  Decreasing  the  lead,  increases  crystallization  and  de- 
creases the  gloss.  Crystals  were  obtained  in  the  presence  of 
0.5  molecule  of  PbO. 

7.  These  aventurine  glazes  did  not  seem  restricted  to  any 
particular  molecular  or  oxygen  ratio,  but  came  within  the 
limits  of  good  glazes. 


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Scope  of  Present  Investigation. 


In  the  present  investigation  an  attempt  has  been  made  to  study 
the  effect  of  variations  in  the  alumina,  ferric  oxide,  boric  acid, 
and  R 0 members  in  a cone  1 aventurino  glaze.  The  correct  heat 
treatmtnt  for  the  proper  development  of  the  aventiirine  effect  was 
also  studied  as  a means  of  control  of  the  crystal  growth. 


lected  as  a basis  of  the  study.  The  investigation  was  divided  into 
two  parts.  In  the  first  part  the  effect  of  variations  in  the  alum“ 
ina,  boric  acid,  and  ferric  oxide  content,  and  the  effect  of  differ 
ent  heat:  treatments  were  studied.  For  the  second  part  of  the  in- 
vestigation, the  best  aventurine  glaze  developed  in  the  first  part 
was  used  as  a basis  for  the  investigation  of  variations  in  the  RO 
constituents  of  the  glaze. 

The  formula  of  the  glaze  under  investigation  with  all  the 
variables  indicated  is  as  follows: - 


were  varied;  the  R 0 was  kept  constant  at  1,0  Na20.  The  series  was 
divided  into  three  groups;  the  first  group  contained  0.05  nioles 
of  Alumina;  the  second  group  contained  0.10  moles  of  Alumina;  and 
the  third  group  contained  0.I5  moles  of  Al^amina.  Each  group  was 


IV 

Method  of  Investigation 

A good  aventurine  glaze  maturing  at  cone  1 (1150^  C)  was  se~ 


0,0  to  1.0  NagO) 


0.0  to  1.0  K^O 
0,0  to  1.0  CaO 
0,0  to  1.0  PbO 


For  the  first  part  of  the  experiment  only  the  ^2^3 


i; 


f 


I 


t 


-9' 


divided  into  a rectangular  field  with  four  horizontal  members  rep- 
resenting variations  in  62©^  content  from  1,25  moles  to  2.0  moles, 
and  five  vertical  members  representing  variations  in  the  Fe^O^con- 
tent  from  0*75  moles  to  0*95  moles. 

V 

Burning 

All  the  trials  were  burned  in  glazed  saggars  in  a down-draft 
coal-fired  kiln,  described  in  University  of  Illinois  Bulletin,  num- 
ber 20,  Vol.  XI,  #44.  The  first  burn  was  conducted  following  the 
time  temperature  curve  of  Fig.  1 so  that  there  was  a considerable 
temperature  difference  throughout  the  kiln.  Cone  pads  were  placed 
in  each  saggar  so  that  the  heat  treatment  of  each  trial  could  be 
noted.  The  effect  of  temperature  variations  was  in  this  manner 
closely  studied.  The  next  biirn  was  conducted  at  cone  3 (1190°  C) 
and  the  final  burn  was  conducted  at  cone  1 with  uniform  heat  treat- 
ment throughout  the  kiln  as  far  as  possible. 

In  the  second  part  of  the  work  the  variations  were  made  in  the 
R 0 members  as  already  shown  and  the  trials  burned  to  cone  1,  A 
representation  of  the  field  covered  by  four  variables  is  difficult 
to  place  on  paper  but  a visual  representation  of  the  field  is  of  a 
pyramid  with  a triangular  base.  At  the  apex  of  the  pyramid,  1.00 
Na20  is  located  with  1.00  KgO,  1.00  CaO,  and  1,00  PbO  as  the  three 
corners  of  the  base  of  the  pyramid.  To  give  a clearer  conception 
of  the  field  covered,  I have  drawn  up  a series  of  tri-axial  diagrami 
representing  horizontal  planes  parallel  to  the  base  of  the  pyramid 
which  indicate  clearly  the  variations  in  the  R 0 members. 

These  glazes  were  burned  to  cone  1 in  glazed  saggars  as  before 


and  the  effect  of  the  variable  RO  members  was  noted  and  tabulated 


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-10- 

VI 

Method  of  Preparing  Glazes  j 

For  the  first  burn  of  the  first  part  of  the  investigation  and  | 
for  the  second  part,  all  the  glaze  materials  were  fritted  as  it  ! 
takes  a long  time  for  the  glaze  to  assimilate  all  the  materials,  ana 
better  aventurine  glazes  are  produced  if  all  chemical  action  has  c 
ceased  before  the  final  fusion  of  the  glaze.  For  the  second  and 
third  burns  of  the  first  part,  O0O5  moles  of  alumina  were  omitted 
from  the  fritt  and  added  as  raw  clay  in  an  endeavor  to  take  advan- 
tage of  the  plasticity  of  the  raw  clay  to  aid  in  keeping  the  fritt 
in  suspension. 

As  most  of  the  glaze  is  quite  fluid  before  all  of  the  more , re- 
fractory materials  of  the  glaze  are  entirely  dissolved,  the  method 
of  drop-fritting  the  glaze  was  not  employed.  The  materials  were 
fritted  in  closed  bottom  crucibles  to  a quiet  fusion  and  then  poured 
into  cold  water  for  quenching. 

After  quenching,  the  fritts  were  ground  in  porcelain  ball  mills 
with  water  till  they  readily  passed  a 100  mesh  screen.  To  keep  the 
fritt  in  suspension  in  water,  the  best  method  devised  was  to  satur- 
ate the  suspension  with  aqueous  ammonia  while  still  in  the  ball  mill, 
Using  this  method  no  difficulty  was  experienced  in  suspending  the 
fritt  in  water. 

In  the  first  part  of  the  investigation,  the  four  corner  fritts 
of  groups  I and  III  were  prepared  as  described  and  all  the  inter- 
mediate glazes  were  prepared  by  molecular  blending.  This  method  of 
blending  is  described  by  Purdy  and  Fox  in  their  work  on  fritted 

glazes. ^5  in  the  second  part,  the  four  corner  fritts  of  the  pyra- 

15  R.  C.  Purdy  and  H.  B.  Fox  "Fritted  Glazes”.  Trans.  Amer,  i 

Cer,  Soc,  Vol,  IX,  1907  P.  9S. 


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-11-  I 

raid  were  prepared  and  the  intermediate  glazes  were  blended  in  the 
same  manner  as  for  the  previous  group, 

VII 

Materials  Used 

The  following  potter’s  materials  were  used  for  making  the 
glazes  and  their  formulae  calculated  as  shown!  | 

Clay  - English  china  clay  #3  - AlgO^ .ESiOg «6HgO 
Borax  - Na^B^O^lO  H^O 
Boric  Acid  - BgO^.  3^2® 

White  Lead  - Pb  (0H)2  - 2 PbCO^ 

Whiting  - Ca  CO^  I 

Soda  Ash  - Na2C0^ 

Potassium  Carbonate  - K^CO^ 

Ferric  Oxide  - Fe20^ 

VIII 

Trial  Pieces 

The  trial  pieces  were  rectangular  biscuit  tile  1 1/2"  x 3" 
manufactured  by  the  U,  S,  Encaustic  Tile  Company  of  Indian^-polis , 
Indiana* 

IX 

First  Part^^ 

AVENTURINE  GLAZE  -Cone  1 

The  variations  in  the  type  formulae  of  all  the  glazes  of  the 
first  part  are  as  follows:- 

I 0.05  - 0*15  AlgO^j 
1 Na20  I 1.25  - 2,00  B20^  | 7«00  Si02 

( 0.75  - 0.95  Fe203) 

An  experiment  conducted  by  the  Ceramics  5 class.  University  of  I 
Illinois,  in  the  first  semester  of  1921-22,  (Summary  by  J . S . Lathrop ) , 


I 


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-12- 

There  are  three  groups  of  glazes  prepared  as  follows;- 

Group  I 0.05  Al20^ 

Group  II 0.10  ” 

Group  III——  0.15  " 

All  groups  used  1.00  NagO  and  7*00  constant  and  varied  as 

follows  in  B20^and  Fc20^ 

R C 


Fe20^ 


0.95 
0.90 
0.89 


0 . 60 


0. 79 


The  figures  at  the  left 
and  bottom  indicate  the  moles 
of  oxide  and  the  letters  at  t 
the  top  with  the  figures  at 
the  bottom  and  the  group  num- 
ber locate  the  glaze  as  IIC4, 
IIIB5,  etc. 


1.29  1 .90  1 . 79  ^*00 

Bp. 

The  tri-axial  diagram.  Fig.  II,  shows  the  small  area  of  Avsn- 
turine  Glazes  figuring  Al20^plus  B20^  plus  Si02  as  equal  to  1.  The 
diagram.  Fig.  Ill,  which  is  an  enlarged  diagram  of  the  portion  of 
the  tri-axial  diagram  of  the  area  of  the  Aventurine  Glazes  gives 
the  location  of  each  glaze  together  with  the  results  of  the  glost 
burn  in  diagrammatical  form. 


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I 
I 


H CO  0-C-'  05  rH  - 0 0 rH  -0  O s5)  CO 

^ tj  1 i rq  cq  "0  rq  O O O O O 

'H  -H  :H  H iH  — I H H H H H M i H H -H 


-13- 

FRITT  FORMULAE  and  COMBINING  WEIGHTS 


lAl 


ia6 


IDl 


1D6 


IIIAl 


IIIA6 


Proportion 

Parts 


Comb  • 
Weight, 


0,05  Clay — 52.0  — 11.10 

0.625  Borax— 954-.0 — 126.00 

0.375  Soda  Ash—— — I59.O — 23.25 

0.950  FepO^ 6OS.O  — — 152.00 

6,900  Flint — 1656.0  — . 4-14.00 

3W.0  7^5 


0.05  Clay- — — 52.0 

0.625  Borax 954.0 

0.375  Soda  Ash— 159.0 

0.750  FepO^— — 4S0.0 
6.900  Flint————  1656.0 

34^.0 


11.10 

126.00 
23.25 

120.00 
414.00 


0.05  Clay 52.0  — — 

1.000  Bora,x — I52S.O — 

0.950  FepO-z-^ — * — 6OS.O  - — — — 

6.900  Flint- 1656.0 

3S44.0 


11.10 

202 .90 

152.00 

414.00 
779.10 


0.05  ’Clay — 52.0  11.10 

1.000  Borax — I52S.O 202,00 

0.750  FesOx 480.0  — 120.00 

6.900  Flint' 1656.0  — — 414.00 

3716.0  T^TTio 


0.625  Borax 954.0 

0,375  Soda  Ash — 159.0 

0.150  Clay— 155.0 

0.950  FepO:: 6OS.O 

6.700  Flint 1 608.0 

3463 .0 


126.00 
23.25 
33.30 

152.00 

402.00 

73^^55 


0,625  Borax — 954.0 

0.375  Soda  Ash I59.O 

0.150  Clay— 155.0 

0.750  Fe«0, 480,0 

6.700  Flint — — 16O8.O 


335^0 


126.00 
23.25 
33.30 

120 .00 

402.00 

704.55 


• AI  '■ 


J- 


“l4-“ 

Proportion  Comb. 


IIIDl 

1.00 

Borax — ^ — — 

0.15 

Clay — 

0.95 

FcpO -7  — — — — — 

6.70 

Flint-——-— 

IIID6 

1.00 

Borax — — — - — »»»— 

0.15 

Clay — — — 

0.75 

FcpO -7 

6.70 

Flint——— 

Parts  Weight . 


152s  .0 — 202.00 

155.0  — 33.30 

605.0  - 152.00 

160s. 0 — te  .00 

3^99.0  7^9.30 

1525.0  — — — 202,00 

155.0  — — 33,30 

450.0  120.00 

l6g0.0  402.00 

3771.0  757.30 


-15- 

RESULTS  OF  GLOST  BURN  Cone  1. 

Glaze 

Cone 

Description  of  glaze  1 

1 

3 

Over-fired, dull, copper  colored. 

2 

OS 

Under-f ired, dull , yellow  colored,  crazed. 

3 

OS 

" , " , yellow-red  color,  " . 

IL 

OS 

” , " , copper  colored,  crazed. 

3 

3 

Over-f ired,bright jbrownish-black  color. 

6 

OS 

Under-f ired, dull, yellow-red  color,  crazed,  j 

7 

3 

Over-fired,bright, mottled  brown  color. 

S 

3 

Over-fired,  " ,dark  maroon  color. 

9 

3 

" , " , Brownish-black  color. 

10 

OS 

Under-f ired, dull ,brick-r ed  color  , 

11 

3 

Bright, deep  brown  color, few  aventurine  spangles. 

12 

3 

Bright , black, speckled  aventurine  separations. 

13 

3 

Bright , brown-black. 

14 

3 

Matt  texture , reddish-brown  color. 

15 

3 

Ower-f ired, dull , copper  color  dappled  with  black.. 

16 

3 

Matt  texture,copper color , bubbled, heavy  aventur-  : 
ine  separation. 

17 

3 

Matt  eggshell  texture , dappled  brown  and  copper 
color. 

IS 

3 

Matt  texture,  copper  colored. 

19 

3 

n tt  n 

» ® 

20 

OS 

Dull, dirty  yellow  color,  crazed. 

21  ' 

05 

Bright , transparent , yellow, white  bubbly  separa- 
tions on  the  surface. 

22 

06 

i 23 

o6 

n 

24 

o6 

" deeper  yellow  color. 

25 

03 

” yellowish  brown  color. 

26 

5 

Bright , yellowish  brown  color , bubbled, crazed. 

!- 

C' 


I 


X 


rf»( 


t 


•r 


r 


\ 


0::; 


-16- 

Glaze 

Cone 

Description  of  Glaze  1 

27 

5 

Bright , brownish-black  color,  mottled  effect* 

2S 

05 

Bright,  yellow  color* 

29 

05 

Bright,  brownish  yellow  color. 

30 

03 

" , yellowish  brown  color,  pinholed,  j 

31 

02 

Bright, dark  brown  with  aventurine  separations, 
pinholed. 

32 

02 

Bright,  mahogany  color, little  aventurine , crazed. 

33 

05 

" ,dark  yellow  color,  crazed. 

3^^ 

05 

",  " , " , bubbled. 

35 

01 

",  " » ^ > pinholed. 

36 

2 

Bright, deep  purple  color , checkered  in  glaze  ef- 
fect,very  fine  aventurine , pinholed, cracked. 

37 

02 

Bright, black  color  with  heavy  separations  of 
copper  colored  aggragates. 

3S 

02 

The  same  with  less  metallic  separations. 

39 

4 

Bright , reddish-black  color  with  white,bubbly 
separations , 

40 

01 

Bright , yellow  color , bubbled. 

41 

05 

Bright , yellow  color, red  aventurine  only  on 
thin  edges , crazed. 

42 

05 

n 

05 

Bright , reddish-brown  color, filled  with  very 
Minute  aventurine  separations , crazed. 

44 

01 

The  same  with  larger  aventurine  separations. 

^5 

2 

Bright, brown  color, heavy  with  aventurine  separa-J 
t ions , beautiful  red  and  gold  aventurine 
spangles  around  the  edges. 

46 

05 

The  same  except  that  the  color  is  darker. 

1^7 

05 

The  same. 

4S 

05 

Bright , orange  color,  very  heavy  and  minute  aven- 
turine separations , crazed. 

49 

2 

Bright, dark  purple  color  with  one  patch  of 

beautiful  red  and  gold  aventurine  spangles. 

50 

01 

Dull,  the  greater  part  of  the  piece  red  and  full 
of  true  goldstone  spangles. 

51 

05 

True  matt  texture , purplish-pink  color,  evident- 
ly a micro-crystalline  structure. 

A*  * 


^'- 


■ 

tf 

Si. 

4k 


> 


t 


ri 


" • '.;<7 


.^0 


. ... ^ . 

' 1 . . _ 
• ■’  j '-  • i , <11  ii;yc 

* 4 » ...  t»  . . • ■ ; 

^ fti/  % «»  ^0 

'.' ' • • V.  j,  »a  ll,  \ £ 


'V"'' 


Glaze 

Cone 

52 

0$ 

53 

04 

5^ 

01 

55 

01 

56 

05 

57 

05 

5S 

05 

59 

01 

60 

04 

-17“ 

Description  of  Glaze 

The  same  but  with  more  of  the  appearance  of 
aventurine  spangles  in  the  glaze. 

The  same  but  lighter  in  color. 

Bright , yellowish-brown  color  with  heavy  aven- 
turine spangles  around  the  edge  and  few 
inside^  crazed. 

Bright,  yellow  color,  aventurine  on  edges, 
crazed. 

Bright, deep  brownish-purple  color  with  very 
minute  and  finely  divided  aventurine 
spangles,  not  crazed  and  a very  attractive 
glaze. 

Matt  texture  but  in  other  respects  the  same 
as  glaze  5^  a-  niuch  lighter  shade. 

The  same  except  a blighter  finish  and  darker 
color. 

Bright , yellow  color  , heavy  aventurine  on  the 

edges  and  very  few  spangles  inside , crazed. 

Bright , light  yellow  color  and  very  few  aven- 
turine spangles , crazed. 


The  diagram  below  show  the  three  groups  of  glazes  with  the 
different  areas  marked  off  on  them. 


Group  I 
0.05  AlgO^ 


Group  II 
0,10  AlgO^ 


Group  III 
0.15  Al^O^ 


B 


C B 


No 

ffych- 

/ 

■GO 

y/es. 

of 

?s 

1 .2^  1 .30  1 .13  2.00 


2 3 


,-./o 


^'9 


111  i . 

.\.a  ^ . 


[s 


I 

i • X « 

w 

...  .‘V  i.r' 

-1.  . 


‘ 


I 


f 

« «■ 

i 

( 

1 

,L. 


I 

L 


-IS- 

Discussion  of  Results 

These  results  indicate  that  with  this  glaze  composition,  an 
alumina  content  of  0,15  equivalents  produces  better  conditions  for 
the  development  of  aventurine  glazes  than  does  a lower  alumina  con- 
tent, The  results  also  indicate  that  the  higher  alumina  content 
produces  more  easily  fusible  glazes  than  do  the  lower  alumina  con- 
tents. This  may  seem  contradictory  to  ordinary  experience  but  the 
results  point  to  this  conclusion. 

The  glazes  with  0*05  equivalents  of  alumina  showed  no  aven- 
turine tendencies  at  all.  This  may  be  due  to  the  heat  treatment 
which  they  received;  all  of  these  glazes  were  burned  either  too 
high  or  too  low.  However,  some  of  the  other  glazes  with  a higher 
alumina  content  which  were  burned  either  excessively  high  or  ex- 
cessively low  showed  brighter  glazes  and  contained  aventurine 
spangles.  One  glaze  alone  in  this  group  showed  tendencies  towards 
the  development  of  aventurine  effects  and  that  was  the  one  highest 
in  boric  acid  and  highest  in  iron  oxide.  This  glaze  only  showed 
the  spangles  under  the  electric  light  and  was  dull  and  unsatisfac- 
tory. 

The  aeea  of  high  iron  oxide  and  mediiam  boric  acid  content 
with  low  alumina  gave  bright  brown  or  black  colored  glazes  which 
lost  their  gloss  on  contact  with  the  air. 

The  group  of  glazes  containing  0,10  equivalents  of  alumina 
developed  all  bright  glazes.  In  this  group  only  the  glazes  highest 
in  iron  oxide  and  highest  in  boric  acid  showed  any  separation  of 
the  iron  from  the  glaze.  In  some  of  these  glazes,  the  separation 
was  thin,  minutely  divided  aventurine  spangles  but  in  one  glaze, 
number  37 j i't  separated  as  large  metallic  separations  which  gave  a 


■ 1 0‘.;“.  •■ 

■ f • r^*‘  1'  T'  , * i*f  • 1 

• V'  • VA  J ♦ » t.'  , 0.  ,i,  i . y •• 

u'v  '.»>•  1.0  i.:nt 

^ %« 

vijp‘  -'X,  “ 

.i'  'i';  . 

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r-  : . t "..■.»  V?  il«  V Ak 

! i-  '••-'f  -Jjl.-'J  '■*1 

-.1 

‘ AiVtaujt/ 


.1 1 cs.r  ';.r,  \ v 


f!ci  j:.d  i ■!■:  ■ .K : \':.i  r;t*i  • u- 


SiDix*  : '.  iZ‘  ":  Vli^g'  .■  fcftSbtlC  ,! 


t 


-->CJvjc»  oc  X'9»'Cr!';  iini.'ju'j..  *c  k:,  < : v i,  pc 

. ■ .’,-bp  e f?  oc  r..‘:;  t.:'  yoA; 


. ii;.  -oj’’-o  .-  i:?;  i.-r  oei  ‘i 

'11  i cc  fu'-*'  ■/’'  ' ! 


. r.:>3  »<ii'iUu  j| 

' '■t'  - 1 r ^ Moc  uiw  V,..;-  i.-  r.v^'  • ....  ; . ; • . ^ ,vc‘l  \o(ll  rfo^.'ivs'  |t 

k 'd' it  n.i.zi.’-*  -j!  * , '.  . c . ; ^ •!  ,/  u£  t*,;  . no  l| 

j.:_  1«J  i;.';  \IC'Vl5  '■  i'ti  XLi  Ifn  i£  ~ : dOO  -•  iliaUjXjB  ■■ 

. , ^ ’ ' 
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«(  :, ; '_:tO)  .:  ■ fiJfiXjji  t ' 


cf  u i ..X  i ,n.  i-  - C . ::s{i  • 


. ‘ X;^ ',» 

I' 


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- ■'••■  ' ks- : I ' » -•  - .«  ;.-i  •*•  \l  *i  .biw  Sfiu^^iiaJQU  niSr  ' 

■>"='  I 


t ■■  i'  iv.  r,i*u'-'  ?:/;'■  * r.o'lt,  /f.ii.'i  lo 

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1 ! w * . . 


rt 


0 "O  fifeO*^ 

.,^  'io  ]i^ 


:,a  -J  i i: 


■•*•  • f *'•■  £'•  ..  ' i/.u  O. 

X;^  ;^rI;U  ;.?f  .Ci 

n f' 

^ c:c'.i;  .•.•.".vcjeti  Vi.'  £>£(;x  oi'::  *;  n I;  ocoi£:i;-'  Ins:  . :..o  .o  li  pit 


h -' 


r.Tiv  yX.'i'  .'ii' 


n i r : 


f>iiC  ^ ly  ?».( oit  u ' . ‘■Is;  ..;.  *i'.  <..c-Trl  tdS 


\ 


' &f  V n.' V . iiSrtlvif:  v£«Cun£je  ^ c-^w 


MfC 


Ai  f 1 


-19- 


rather  attractive  glaze  but  not  of  the  aventurine  effect.  The 
color  range  does  not  seem  to  be  uniform  except  that  the  glazes  high 
in  iron  oxide  and  low  in  boric  acid  and  those  low  in  iron  oxide 
and  high  in  boric  acid  were  lighter  colored  than  the  others.  The 
other  colors  were  dark  yellow,  brown,  black  and  purple. 

i 

The  group  containing  O.I5  equivalents  of  alumina  showed  the 
greatest  tendency  to  produce  aventurines.  All  of  these  glazes  ex- 
cept the  ones  high  in  iron  oxide  and  low  in  boric  acid  and  those 
high  in  boric  acid  and  low  in  iron  oxide  showed  more  or  less  aven- 
turine spangles.  These  excep^tions  produced  yellow  colored  glazes 
while  the  others  produced  darker  colors.  The  glazes  lowest  in  iron 
oxide  and  lowest  in  boric  acid  showed  the  best  aventurines,  produc- 
ing large  patches  of  the  true  red  and  gold  goldstone  effects.  In 
this  group  the  glazes  highest  in  iron  oxide  and  highest  in  boric 
acid  had  a tendency  to  produce  matt  textures. 

In  all  the  groups  the  glazes  highest  in  iron  oxide  and  lowest 
in  boric  acid  and  those  highest  in  boric  acid  and  lowest  in  iron 
showed  more  of  a tendency  to  craze  than  the  others. 

One  peculiar  effect  noticed  is  that  in  each  group,  the  glaze 
with  the  highest  iron  oxide  and  highest  boric  acid  content  pro- 
duced a bright  brownish-purple  colored  glaze  which  had  a good, 
glossy  finish  and  good  texture.  This  color  grew  darker  as  the 
alumina  content  increased.  The  glaze  of  this  composition  in  the 
O0I5  alumina  group  was  the  best  colored  and  finished,  being  glossy 
and  smooth  with  no  pinholing  or  crazing.  It  was  uniform  in  color 
and  texture  and  was  thick  with  very  tiny, minute  aventurine  spangles  I 
which  did  not  show  up  well  except  xinder  the  electric  light.  The 
glaze  developed  well  clear  down  to  the  edges  of  the  piece.  It  dev- 


^ v;:  f.;  ;; 

^(5!  ^ '-'i  :^; 

':<i  i 'i  ■ i.  I Si  i 

. rx  ..  . r . .;  ' - - t ^ t . 

r ' i rusits  jit:. 

' n . 

t.;'  ; . 

. . ■ r 'i  ;■  t (.  i , 

- ' • c vj;  I L*»Y  , 

'i  is  <|I  '■' • WOi  D.*-..;!.  fr 

(-■  . , l '|  . ■ s'^  I ' ■ V . , ’ i 


;ii  o r....  r r V- Osii^a  iv 

t'lj  c j v.>:i  u *io£6o 

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' ICJ,  - 

■ :,  -'ir  'I  'tdj'i,  •_• 

ui't:lr^tp?Tvc.5^.  :.'r'j.v  ttrfT'  - 

>1  /J  \:  •.■.*<■  .:  . wi;  * 

.•  ^ »<3  • -'cnc  * J. . , r.. t> 

. >Xrg§  - s'.f  ill  :i>  i ; 

' , •■ji.-ifLi  onxv.;;^ 

. - j .- . «*■  'c>  ♦i^.iii. 

i -eljiro 


. -.‘OtVir  . -J  airij  •\.  xfei  w:i 

■’  .it.  : • •'  ' c/  XiSv*  uvTi  L Ti  .>•»  ■''  t •r.*'  j - . -i 

* • J <-rr.  . : v".^oij|a(|si  tZ'C 

— v~  •'-L  t .....  , :*■'  ■•  ■.  ■;  : I ’ o '.  xXi‘  cl 

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♦ - rj  .-  .ru-ij  .1  •- S _ ‘i’c;a  L-j-r'^ru. 

jSkw  ; 'j  .' .'*j  ; . ,•  £1  Mjx  .'j”'.,*  i.'J.  ?t  :'.e--.!-jr:  oc. . r:aC;- 

-■•i-  i v,  ^ ‘ M V'lt  rfj  t» 

t --  !».'•  ^ ' I , , ,..  _ : irr«ji:7.:^  i bb^:rt 

Pfi’lt  <Lk  ' ‘.Xii  v"‘i^  'i  ‘i  .<’'••  , *i‘  « <T  t"’  .i-r^  *T''  (••  ^COXj 


' ■'•c  sirfs''  'rr,  £ • . ^ .‘i t w:'.' i. 


•r.ol<:o  I't 

'».' r-  V 

T > V - i : 4 Of?  ifi’  f 

.-.-J 

(fi 

-'•  -S  fjfli*:-' 

% 

■ . > V V iJlv  .oifi.,  'X  rr 

'LiJ- 

&iUI 

':X'i  if  otiio  . V 

"I'-’i.-  . sty,.-.,  xf!W  tircilrj  o(;.G 

•tiidw 

c Vr-'  . . 

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i”  t ::  t 

V • '*  iJCrTf?  x,:©sl01' 

trk  «M 

-20- 


eloped  at  cone  05  and  makes  a very  pleasing  glaze. 

The  heat  distribution  through  the  kiln  was  not  uniform  so  the 

heat  treatment  of  the  glazes  varies  and  it  is  hard  to  draw  conclu-  i 

! 

sions  as  a result.  | 

Some  of  the  glazes  were  dipped  too  thick  and  others  too  thin. 
Most  of  the  glazes  showed  improper  blending  of  materials,  j 

With  these  handicaps  it  is  hard  to  draw  any  uniform  conclusions 
from  the  results.  The  heat  treatment  given  the  kiln  seems  to  have 
been  poor  and  the  cooling  especially  seems  to  have  been  too  rapid 
for  proper  development  of  aventurine  glazes. 

Conclusions. 

1.  0.15  equivalents  of  alumina  gives  a better  condition  for 
the  development  of  aventurines  than  a lower  content. 

2.  A low  iron  oxide  together  with  a low  boric  acid  content 
in  this  glaze  with  highest  alumina  content  produces  the 
best  goldstone  effects. 

3.  High  iron  oxide  content  with  high  boric  acid  in  the  high 
alumina  glaze  tends  to  give  matt  textures. 

4.  High  iron  oxide  with  low  boric  acid  and  high  boric  acid 
with  low  iron  gives  yellow  glazes  with  crazing  tendencies, 

5.  Increasing  alumina  content  gives  more  easily  fusible 
glazes. 

6.  The  best  temperature  to  develop  these  aventurines  is  cone 
1 or  cone  2* 

7.  * A good  bright,  brownish  purple  glaze  maturing  at  cone  05 
is  developed  with  0.I5  alumina,  0.95  iron  oxide  and  2.00 

boric  acid  in  this  base  glaze. 

S.  The  glaze  blending  and  heat  treatment  must  be  accurate 
carefuiiY  aventurine.  glazes. 


*.•  QOXll 
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V*  • 


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I'  -•  ...  .,  .•  ,. 

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. 4 i 


.'/fe’i  I.  •.  .' 


'■4  ilcX.’kvc  ■,  • % I'jc  * 

■ ,'Ii'^  ■^  ' . L5-  *«0  JMH 


1 


-^.1 


. f.  f: '*r.' 

I ...  . 


y.i;  .-<  <*(®  . ..  ..  8,  _js 


tl'7 

■ r.  . .-, 


■ *'  . » • •^■JV  'J,  t,  . J; 


-21- 

Cone  3 (11900  C)  Burn 

The 

glazes 

used  in  this  series  were  the  s^-me  as  those  used  for 

the 

first 

burn 

except  that  0.05  moles  of  Alumina  were  left  out  of 

the 

fritt 

and  added  to  the  glaze  later  as  raw  clay  in  an  attempt 

to 

take  advantage  of  the  plasticity  of  the  raw  clay  to  aid  in  hold- 

ing  the  fritt  in  suspension. 

The 

glazes 

were  burned  to  cone  3 glazed  saggars  as  before  | 

and 

the  results 

are  tabulated  below.  j 

RESULTS  OF  GLOST  BURN  - Cone  3. 

Glaze 

Cone 

Description  of  glaze 

1 

2 

Light  brownish  purple,  large  metallic  separations J 

glossy. 

2 

1 

Light  brownish  purple,  minute  aventurinr  crystals j 

glossy. 

3 

1 

N 

k 

2 

Light  red  color,  good  aventurine  separation, dull • 

5 

3 

Brown  to  black  color, red  aventurine  separations 

on  edges,  dull. 

6 

1 

P\irple  color, minute  aventurine  crystals , glossy . 

7 

3 

Golden  color, heavy  metallic  separ actions, dull. 

2 

Purple  to  golden,  heavy  aventurine  separations. 

glossy. 

9 

3 

Golden, heavy  aventurine  separations,  dull. 

10 

3 

Dirty  golden  color, good  aventiirine  separations^on 

edges , dull . 

11 

4 

Reddish  gold  color , entirely  crystallized, dull , 

overburned. 

12 

4 

H 

13 

4 

tl 

: 14 

4 

It 

1 15 

3 

Reddish-brown  color, heavy  aventurine  separations. 

dull. 

- 16 

3 

Reddish-brown  color , metallic  separations ,dull . 

17 

3 

" ,beautiful  aventurine  crystals 

on  edges , bright 

-nTV. 


. ...  i.,  r-'f ' 


\\X  , 


..•■»'  r-\. 


: V:? 


nA 


e£SC 


J M ' -t  . • 


JScivi  ftiki: 


1 

r i c.  C . \ 


fi- .'  • '.P.-  -;ai 

;;: 

c:  V t' 

' ; 

■ -r-'-T'"  L.  ■ 

• I-.  I ■ "'V.ii',  fj  i 


:.  ,*'y  ;..'i  v. 

r*j  '■ . 'i  • >.  o "■ 


I .. 


v:  . ‘J. ..  _ i 


> 


r:  - 

L.^,'  > ‘ 

r.;* 


i J /■  :; 

. . ' ■ I ■ ‘ ' 

„ .J 


,.  S ;> 'i  ' 


XTivy?  - r<%V«-j  Y 


Jj  i , l‘  i V "J  •"  ft . i *1  <• 1 1 1*  ■'  • ■ !.  ■ '.! 


<**««>»• 


; 

.i 


. ■ i I 


Glaze 

Cone 

-22- 

Description  of  elaze 

Ig 

4 

Reddish  golden  color,  entirely  crystallized, dull , 

19 

4 

over “burned. 

20 

4 

Red  to  black  color,  heavy  aventurine  separations. 

21 

03 

dull. 

Light  brownish  purple  color, no  crystals , bright . 

22 

03 

n 

23 

03 

« 

24 

03 

n 

25 

01 

Black, few  metallic  separations,  glossy. 

26 

3 

Yellow, entirely  crystallized, dull, overburned. 

27 

4 

Muddy  gray  color , entirely  crystallized, dull , over- 

2g 

4 

b\irned. 

n 

29 

1 

Reddish  gold  color  , beautiful  crystals , dull . 

30 

3 

Mottled  gold  and  black , metallic  separation,dull . 

31 

3 

Reddish  color , entirely  crystallized,  dull,  over- 

32 

02 

burned. 

Muddy  purple  color , metallic  separations,  dull. 

33 

01 

under-fired. 

Purple  to  golden, heavy  aventurine  separations. 

3^ 

< 1 

glossy. 

n 

35 

2 

Mottled  red  and  gold, heavy  metallic  separation. 

: 36 

3 

dull . 

Dirty  golden  color , entirely  crystallized,  dull. 

37 

02 

overburned. 

Dark  purple, golden  aventurine  crystals , glossy . 

3S 

3 

Red  to  golden  color,  entirelycrystallized,dull. 

39 

3 

overburned. 

n 

40 

2 

Red  to  black  metallic  and  aventurine  separations. 

1 4l 

03 

glossy. 

Dull  reddish  brown  color, no  crystals , semi-glossy , 

42 

02 

Brownish  purple, minute  aventurine  crystals,  semi-  : 

1 

glossy. 

Golden  brown  color, heavy  minute  crystals , glossy , 

44 

1 

Brownish  purple  color, few  minute  crystals , glossy . 

Glaze  Cone 

-23- 

Description  of  glaze 

^5 

1 

Golden  red  color , beautiful  aventurine  crystals. 

46 

2 

glossy. 

Dark  gray  color , aventurine  separations , dull , over- 

1^7 

02 

burned. 

Purple  color, no  crystals , glossy , under-fired. 

4S 

02 

Purple  gray, shows  tendency  to  crystallize , glossy . 

49 

02 

Purple,  no  crystals,  glossy. 

50 

1 

s 

Reddish  purple, good  aventurine  crystals, glossy . 

51 

3 

Golden  black  color , metallic  separations , dull. 

52 

01 

overburned. 

Grayish  purple, few  aventurine  crystals , glossy . 

53 

01 

Purple  color,  few  aventurine  separations , glossy . 

5^ 

1 

Purple  to  golden  red, heave  avent\irine  separations. 

55 

1 

glossy. 

Purple  to  dark  red,  beautiful  aventurine  separa- 

56 

2 

tions,  glossy. 

Dull  black, few  aventurine  separations , semi-glossy i 

57 

2 

Dull  black  to  golden, heavy  aventurine  separations! 

5S 

1 

glossy . 

Purple  to  golden,  heavy  aventurine  separations. 

59 

1 

glossy. 

Purple  to  red-golden, heavy  aventurine  separations  , 

6o 

2 

glossy. 

Red,  mottled  metallic  separations , dull . 

Discussion  of  Results  of  Cone  3 Burn. 

The  conclusions  drawn  from  the  first  burn  are  pretty  well  demon-' 
strated  by  this  burn  to  be  correct.  Evidently  cone  3 is  too  high  a 

temperature  for 

these  glazes,  as  most  of  them  are  overbiirned.  One 

point 

is  brought 

out  quite  strongly  by  this  burn  and  that  is  the  ef- 

feet 

of  alumina 

on  the  development  of  aventurine  crystals.  The 

glazes  in  Group 

I with  only  0»05  moles  of  alumina  are  nearly  all  of 

! them 

entirely  crystallized,  indicating  that  the  glaze  was  quite 

fluid 

at  cone  3 > 

thus  allowing  heavy  crystal  separations.  The 

glaze 

in  Group  III,  on  the  other  hand,  have  not  crystallized  so 

f 

t 


*>  ■ .A- 


f/b 


1 4 fci  i.  , 

_ _ i.  ' ^ ' • . J.  I,  i jt'  w'  Jl!  i j '.'  '. 

I t,.  . ..  ■ . ’.■•>  •_  i T._  ■ 

\ ^ ^ ^ t ('  \ \ 1 t ' • 

. V . If.  f..'  ■ 'i'  ' 

► ■•':»-  J - ri  : : 1,  ■. 

r * i '■  " *:•<"  i x .-  ’ 

-f t.  ’ ■ 

,-•  I:  ■ ' «4.'‘  t ■ / ■- t f 

‘ j . V r-r  t 'i..  I 7oVii  ,■  . 


I : f 


ivT*  *•  . 


w 'll  V iJ  i,  ' 


. - cwt' 


0 


; I I 


i ■ . ( 


♦V  ■ 

. <,  > ^ Oi  J 


- »'CO  I 

.V 


j fmwA 


'U  H 


I 


::el 


r'  Yi.;;  ^ c.i*  ii  c : If.':;,  v ’.i  . ; ■.r'4.v 


»-  il'.-  1 iXr.i  J 

• -i'i  iTU. ''.t  fir*  ; 


>■ 


. Wf!*i-  ' - • 


f*  .. 


.-Is  c £*i  : ; Lr  / i.h  \ - . i : 9^1:'^-.  fac  : 

)',  e?tT  . :r- ;*!»/•;  -.j -r'iVi;  I .*  .. -*tk.v  -.'3  r... 

I o i,l.v  v.fi....-r*:  rvniirti  Z:  "ic  Cifllciv  * .; s"il^  T 

! i i 'gffi-;*  "iX-fri,  • ^jr‘.Ls:  i'.  . : yi 

* s. 

li 

I *;r.  ; tl  l£j<dVic  w cn  , ' 7srfJO  e^Si’ 

' - r r, '-t;..:  i r-s-  -..  .■■•js-yafiXTyar 


. < 


'id  '■■•i; , .-'■  'I 

, 1' 

. r.;:-'ruXfii  ;.  cs': 

■ ■'*  -1 

I'O’iO  .'i  jj 

o v;'- 

' D.TO'J  JJ'J, 

-. ' i:  ii 


-24- 

heavily,  indicating  that  the  glazes  in  this  group  were  more  vis- 
cous at  cone  3 and  did  not  permit  of  such  heavy  crystallization. 
The  glazes  of  Group  II  are  intermediate  in  this  respect. 

The  tendency  of  the  AlgO^  seems  to  be  to  give  a deeper  and 
richer  color  to  the  glaze  as  the  quantity  increases  as  well  as  to 
decrease  the  fluidity  of  the  glaze. 

The  glazes  with  lowest  iron  and  lowest  boric  acid  content 
seem  to  give  the  best  aventurine  crystals. 

Conclusions  from  Cone  3 Burn. 

1.  Cone  3 is  "fcoo  high  a temperature  for  these  glazes,  and 
is  likely  the  proper  temperature  at  which  to  mature  these 
aventurine  glazes, 

2.  Low  boric  acid  and  low  iron  give  the  best  aventurine 
crystals , 

3.  The  other  conclusions  of  the  first  burn  are  verified 

Third  Burn  of  First  Part  - Cone  1, 

This  series  was  the  same  as  the  second  series  but  was  burned 
at  cone  1 with  careful  heat  regulation  and  with  a little  longer 
time  allowed  for  the  maximum  ten5)erature . 


f X > 


’•..‘Jii;  L-t  v„.c^ 

'■V  •:;*■ 


/ i-  ' > . r ■ 


..  r *;  V A 4 

tXil-  !-  I 


& iMo 


. «••  e ' ^ 


‘^inV  wi  .'Ci.'.;. ■..c ■ 4 jLtj.  li  v’'*'’-' 


yl^j  er: 


6-y  : ;:  <,  • £'  f 'iii  'iw  ..Jt 


. : f IT  c • i . > ‘ *! 


■ \ 


j t •■ 


. t 


r,:-'-3  ...  ..o  ,v  Iftifoi'j 

;.X)  ic  atU  . 

ao5  i i' . i ' :■  X .>  (•  i; j I j ex(T 

; 'jw  ru*“  V t;  . (,^.2  ifvijj,  cc/ 


. r''  ' ' ■ ' •■■■' 

»4?-..i,L3  .....  . . ■•;£;•'  t;<:4  nl  , '/i4'*0 

X X.  .’iT  C3  . X X :■:  : .<4  V C^J^i.X 


i 


1i  .T.'re)  ■ ■ •■X  -V*;,  r.v'T.*  cic.  4 

, "-rfvia 

*( 

’ 1 . : 'i.  . il'i.J'rf  o4»‘.  i'J  ;•  » i"i»  lv'> 


■ H X t ■■ 


.tft 


w 


f ■ f 


vXi  i’i-.'O 


t>  w <?  • '.  * .-I 

. I it*  » # 


*Xl4T 


•4!^. 


'■*'  ‘.l9n^  I.  arroc 


« \ ' M ' w i*  ..  C-  V . ^ . ••  • i«  /> «' 


X^irftXXjl 


Glaze 


Cone 


1 

01 

2 

01 

3 

02 

4 

1 

5 

1 

6 

1 

7 

1 

S 

2 

9 

2 

10 

2 

11 

2 

12 

2 

13 

2 

i4 

2 

15 

2 

l6 

01 

17 

01 

IS 

1 

19 

2 

20 

1 

21 

03 

22 

03 

23 

24 

1 

25 

1 

26 

1 

-25- 

Results  of  Burn  at  Cone  1 (1150®C) 

Description  of  glaze 
Purple  color,  no  crystals,  glossy,  crazed.  j 

” , few  minute  crystals,  glossy , crazed.  | 

",  " , dull,  crazed.  ! 

l 

I 

Golden  red,  almost  entirely  crystallized,  dull. 

Reddish  black,  beautiful  aventurine  crystals, 
glossy. 

Brownish  purple,  heavy  with  minute  golden  crystali 
glossy. 

n 

Golden,  entirely  crystallized,  dull. 

> f • 

Red-golden,  entirely  crystallized,  dull. 

H n ft 

n M « 

* » • 

Golden,  entirely  crystallized,  dull. 

n w n 

» > » 

Brownish-red,  entirely  crystallized,  dull. 

Brownish-black,  few  metallic  separations,  glossy. 

Brown,  few  metallic  separations,  glossy. 

Brown-red,  patches  of  good  aventurine  crystals, 
glossy. 

Brown-red,  entirely  crystallized,  dull. 

Purple-black  to  golden,  heavy  with  minute  crystal^ 
glossy. 

Red,  no  crystals,  not  developed,  dull. 


Light  golden,  almost  entirely  crystallized,  dull. 
Gunmetal  color,  patches  of  good  crystals,  glossy. 
Red-p\irple,  no  crystals,  glossy. 


— 26“* 

Glaze 

Cone 

Desdription  of  glaze 

27 

1 

Red-purple,  no  crystals,  glossy. 

2& 

1 

Gray -purple,  minute  aventurine  crystals,  glossy. 

29 

2 

Red-golden,  entirely  crystallized,  glossy. 

I 

30 

1 

Black,  beautifully  crystallized,  glossy.  j 

31 

1 

1 

Red-purple,  no  crystals,  glossy,  crazed. 

32 

1 

n n n n 

f » » • I 

33 

1 

Red-purple,  few  minute  crystals,  glossy,  crazed. 

3‘^ 

1 

Red-purple  to  golden  aventurine,  glossy. 

35 

1 

Black,  metallic  separations,  glossy. 

36 

1 

Red-purple,  no  crystals,  crazed,  glossy. 

37 

1 

Dark  purple,  no  crystals,  crazed,  glossy. 

3S 

1 

Gray -purple,  minute  crystals,  glossy. 

39 

2 

Golden,  entirely  crystallized,  dull. 

4o 

1 

Black,  beautifully  crystallized,  glossy. 

41 

03 

Dull  brown,  no  crystals,  dull,  underfired. 

42 

1 

Brown-purple,  no  crystals,  glossy,  crazed. 

1 

Purple,  minute  crystals,  glossy. 

44 

1 

Gold-purple,  many  minute  crystals,  glossy. 

^5 

1 

Red  beautiful  aventurine  crystals,  glossy. 

46 

1 

Purple,  no  crystals,  crazed,  glossy. 

; 47 

1 

n It  n « 

» » » • 1 

4S 

1 

It  n It  n 

> i i • 

’ 49 

1 

It  II  It  It 

» > » • 

50 

1 

Red-brown,  heavily  crystallized,  matt  texture. 

' 51 

1 

Red,  no  crystals,  glossy,  crazed. 

52 

1 

Mottled  purple , no  crystals,  glossy. 

53 

1 

Red-purple,  no  crystals,  glossy,  crazed* 

JCS: 

II 


Ci 

i 


> - '.  ■•  'xo  a - , 

^ w - * . - • 

- 

: . \ fin 

c iOAid 

i 

'‘I  -:s 

t , 

r 

>v'.x^ 

W ^1! 

1 

••  ^ 
t 

£ 

A ■ 

i 

S 

, . 1 

'■  4 r f ' . . . •-,  f.;i 

JL 

i 

V 

..idffjk 

J 

t-C 

t ^ 

V . 

'■ ' 1 i i?  X'  'i .'  n r :•.  . 

cc 

1 

4 Z\1‘.  ^ . •,  V t ' ' 

-4  . 

, 

-•.  -ii  , „..•  . 

i 

' 

>.  4 “ ■ i ' '_ 

l‘ 

h 

■t 

\ ' 

1 '.  i'-  . . 

- * j_  . ^ ' *■  J. ' , 

1 

t ^ 4 « jT  .■•.  w ^ •;  'i 

• 4'.  - , . , uX'.( 

CO 

• s • •- 

• 4 

- ***y  ^ ^ \ 

•m 

U‘ 

* , ' ^ ‘ 1 • 

- •.'  '! 

; 

• « 

r I 

. '^ ',.  '.1  ■ ’ . ’ • 1 V 1 , A t 

. 

4 , i ";  ■ f, 

4i^ 

oV*A 


;j 

i " 


I ^ 


. •<»4 


f 


i I 

't 

t ^ 


t 


i : 


r 

1.  >1-  V, 


t 


V 


t 


I • 


t 


’<  " 

( 

M 

*'  It 

I 

"i  I » ' i ••  ' ‘ 

. '•  LfC- 


-•.  i. 


-27- 


Glaze 


Cone 


Description  of  glaze 

Red-purple,  no  crystals,  glossy,  crazed, 

” ,few  minute  crystals  , glossy,  crazed. 


54 

55 

56 

57 

5S 

59 

60 


1 Purple-red, no  crystals,  glossy,  crazed 
1 Red-p\irple,  " , ",  " 

1 Purple,  no  crystals,  glossy,  crazed. 


1 Red,  no  crystals,  glossy,  crazed. 


1 


1 


1 


n 


> 


n 


n 


n 


Discussion  of  Results  of  Third  Burn  (at  Cone  1.) 

As  in  the  previous  burns,  the  higher  alumina  content  gives  a 
more  viscous  glaze  and  retards  crystallization  to  a very  marked 
degree.  The  temperature  of  this  burn  is  evidently  the  proper  mat- 
uring temperature  for  these  glazes  as  most  of  them  turned  out  glossy 
and  smooth. 

The  low  iron  and  low  boric  acid  glazes  give  the  best  aventur- 
ine  crystals,  and  the  most  beautiful  glazes.  Increased  iron  con- 
tent seems  to  give  the  glaze  more  of  a red  color  than  the  lower 
iron  content , 

When  these  glases  do  not  develop  any  aventurine  effect  they 
nevertheless  produce  beautiful  mottled  purple  colored  glazes. 

Conclusions  from  Third  Burn  (at  cone  1) 

The  conclusions  drawn  from  this  burn  coincide  with  the  conclu- 
sions of  the  two  previous  burns. 

General  C onclusions  on  Effect  of  Heat  Treatment  and 
Variations  in  the  content  of  Aliimlna,  iron  and  boric  acid. 

The  general  conclusions  drawn  from  the  foregoing  work  are; 

1.  Aventurine  glazes  with  these  variable  compositions  mature 


w 


t'V=^  ^0  ^ • . .'  '^X  i - 1 

j,  “ a {. 

'¥ 

C 

M ’ »* 

4 « . X 

' . -fctfK 

X 

: ' 

V.  ' . 1x1  *i 

X ''  ■*". 

) 

t 

•f*  , ) 

v<.;  1 

. ■’  i;r,'iT  To  b--  ^ ; 

. V I.'..;;  •'ll  43 

! 

1! 

*: 

•■  ■■  ^ ■ f w . 1- i «iA 

1 

i 

- r oj;  .;■  f . 1 V w L'  - 

•1  c V ’a  f '• 

(WOOctV 

|l 

» J 

Vl^W»t>iV0  CIS  L'l-  '.< 

^C- 

w!  cdT  * 

i 

‘>‘u-fc  yo  sS'Oia  c,*.  QesbXt 

■,  .bjfJ  -wl 

4 «oo«»  ixijj: 

i.' 

->i  - v;  i*v>-n  ? to..  z »,w.^  .■  rfT.  j» 

/<■  . ^9CM  Ti:  ,>  ^ ^j^j.  ^,. 

; ',. 

- 'iv  • •-  • :■■  J :>e8  hlBit. 

‘ . »>C 

jj  ^r*'*  '--  ‘,ic>  T : V ; •<  . i:,n  bb  worn  '.  --^^j 

« ■■■  • '’'ivl.-c  ‘A  *•■"■’  '1'.  i.  i!  :'.^T  - ; •.  «.- ' 

* j 

( <■  ; ut-O  >'•<.•)  ijiax’S  in  ;.  .kC  i":  ’^T'C  I ■■-ti /'•;''  .,  ’•  .• 

- 'lor  . t ••  J ■ ■■  ■ •'  •:  a . •'  i':H:Xa4icc  VtfT  c.’i’  !• 

avolv—K.  owj  "tc  u , 


> ' # 

» . i .0  . ^ 

. out,,.,,'  ^\inCu.'X^‘i  t 


-2S- 

at  cone  1 • 

2.  Increasing  alumina  content  retards  crystallization, 

3.  Best  aventurine  glazes  were  obtained  with  low  iron  and  low 
borid  acid  content. 

4.  Least  crazing  was  found  in  areas  of  maximum  crystalliza- 
tion. 

5.  In  areas  where  no  crystallization  takes  place,  beautiful 
mottled,  glossy  glazes  are  produced  with  a rsd“p\irple  color 

6.  To  produce  the  best  results,  the  glaze  materials  must  be 
entirely  fritted  together  before  being  applied  to  the  piece 

7.  Careful  blending  and  careful  firing  and  cooling  must  be 
regarded  for  the  proper  development  of  aventurine  glazes, 

S.  The  best  aventurine  glaze  produced  has  the  following  com- 
position; 


(0.15  AI2O3) 

1.00  Na20  (1.25  B2O3  I 7.0  Si02 

(0.75 


Part  II. 

In  the  second  part  of  the  investigation  an  attempt  was  made  to 
determine  the  effects  of  variations  in  the  R 0 group  on  the  devel- 
opment of  aventurine  glazes  and  their  maturing  temperature.  This 
was  accomplished  as  outlined  in  the  Method  of  Investigation.  The 
tri-axial  diagrams  showing  the  R 0 composition  of  each  glaze  are 
given  in  diagrams  V,VI ,VII ,VIII , and  IX. 

The  method  of  preparing  the  glazes  and  of  blending  is  the  same 
as  given  for  Part  I,  Series  I and  the  firing  was  carried  out  to 


t 

( 

( 


. 1.1 


,^•c  ••  ■ ■ • . . • ; -1  . r \ r ..  ..  . 7f  i'r;l  'j 

....  . ; ■ ' ■ . . ; *■'  I 'V-jCnz.  >i 

i • f.3:  . V''..'!  T'  f A X/t‘  «JW»  ■■; 

• . • o . '■  V ■; 1'e  rtt  ii-Ir 


-29- 


cone  1» 

The  glaze  formula  with  the  R 0 variations  used  in  this  work 
is  as  follows: - 


0.0  to  1.00  Na  0 
0.0  to  1.00  K26 
0.0  to  1.00  CaO 
0.0  to  1.00  PbO 


) 0.15  Al-0,) 
) 1,25  B2^0i) 


0-75 


Fc20^) 


7.0  SiOg 


The  glaze  compositions,  batch  weights,  and  RO  components  of 
each  glaze  are  given  in  the  following  tables. 


Glaze  composition  and  Batch  Weights 


Glaze  1: 


0,70 

0-75 

Glaze  362 

1.00 

0.15 

6.70 

1.25 

0,75 


Glaze  51 : 

1.00 

0.15 

6.70 

1.25 

0,75 


Glaze  56: 

1.00 

0.15 

6.70 

1.25 

0.75 


0.625  Borax — - — - — 1906.O  — 

0.375  Soda  Ash-—- 31S.4 

0.15  Clay- 309.6  

Flint— — 3216. Oir 


Fe203‘ 


KpOOt- 

Clay^-" 

Flint- 


Comb  • 
Weight. 
— -126,00 

— 23.25 

— 3^.20 

— 402.00 

120  .00 


Whiting" 

Clay 

Flint— 

®2®3 

Fe203 — 


6712.6 

1104.0 
309.6 

3216.0 

700.0 

960.0 
62^9.6 


70^5 

94.00 

34.20 

402.00 

67.50 

120.00 

737.70 


600.0  56.00 

309.6  — - 3^.20 

3216.0  — 402.00 

700.0  — — S7.5O 

960.0  — — 120.00 

5935. 6 699.70 


mte  lead- 

Clay — 

Flint—" 
B2O3 — 

*3“^’ — 


Fe  gU- 


1035.0 
309.6 

3216.0 

700.0 

960.0 


223.00 
34.20 

402.00 

67.50 

120.00 

msTfu 


I 


f 


r\ 


I? 


I 

I 


\ 


> 


-30- 

RO  Component 3 of  Part  II 


Glaze  RO  Components. 


1 1,00  Na20 

2 o.S 

Na20,  0.2  K20 

^ 0.6 

Na20,  0.2  CaO 

4 0.6 

Na20,  0.2  PbO 

5 0.6 

Na20,  0.4  K20 

5 0.6 

Na20,  0.2  K20 

, 0.2  CaO 

7 0.6 

Na20,  0.2  K20 

, 0,2  PbO 

g — 0.6 

Na20,  0.4  CaO 

^ 0,6 

Na20,  0.2  CaO 

, 0.2  PbO 

10 — — — 0.6 

Na20,  0.4  PbO 

11  0.4 

Na20,  0.6  K20 

12  — — 0.4 

Na20,  0.4  K20 

, 0,2  CaO 

1^ — 0.4 

Na20,  0.4  K20 

, 0.2  PbO 

l4  0.4 

Na20,  0.2  K20 

, 0,4  CaO 

15 0.4 

Na20,  0.2  K20 

, 0.2  CaO, 

0,2 

PbO 

16  0.4 

Na20,  0.2  K20 

, 0.4  PbO 

17  — 0.4 

Na20,  0.6  CaO 

IS 0.4 

Na20,  0.4  CaO 

, 0.2  PbO 

19  0.4 

Na20,  0.2  CaO 

, 0,4  PbO 

20  0.4 

Na20,  0.6  PbO 

21  — 0.2 

Na20,  0.6  K20 

22 0.2 

Na20,  0.6  K20, 

0.2  CaO 

23  0.2 

Na20,  0.6  K20 

, 0.2  PbO 

24  — 0.2 

Na20,  0.4  K20 

, 0.4  C aO 

25 — 0.2 

Na20,  0,4  K20 

, 0,2  CaO, 

0.2 

PbO 

26 0.2 

Na20,  0.4  K20 

, 0.4  PbO 

27 0.2 

Na20,  0.2  K20 

, 0.6  CaO 

28 0.2 

Na20,  0.2  K20 

, 0.4  CaO, 

0.2 

PbO 

29 0.2 

Na20,  0.2  K20 

, 0.2  CaO , 

0.4  PbO 

30  — — — 0.2 

Na20,  0.2  K20 

, 0.6  PbO 

31  0.2 

Na20,  0.6  CaO 

32 0.2 

Na20,  0.6  CaO 

, 0.2  PbO 

Na20,  0.4  CaO 

, 0.4  PbO 

Na20,  0,2  CaO 

, 0.6  PbO 

35 0.2 

Na20,  0.6  PbO 

36  1,0 

K20 

37 0.6 

K20,  0,2  CaO 

3S ...  0.6 

K20,  0,2  PbO 

79 0.6 

K20,  0.4  CaO 

4o  — . 0.6 

K20,  0,2  CaO, 

0.2  PbO 

4i  — — — 0.6 

K20,  0.4  PbO 

42 0.4 

K20,  0.6  CaO 

43 ...  0.4 

K20,  0,4  CaO, 

0,2  PbO 

44 — 0.4 

K20,  0,2  CaO, 

0.4  PbO 

45 0.4 

K20,  0.6  PbO 

48 0.2 

K20,  0.6  CaO 

47  ... — ..  0.2 

K20,  0,6  CaO, 

0.2  PbO 

4g 0.2 

K20,  0,4  CaO, 

0.4  PbO 

49 0.2 

K20,  0.2  CaO, 

0,6  PbO 

50 — 0.2 

K20,  0,6  PbO 

4 


- ■''  ( 

-31-  1 

Glaze 

RO  Components 

51  — 

1.0  CaO 

52 

O.S  CaO,  0.2  PbO  ] 

p 

?3 

0.6  8aO,  0.4  PbO  j 

p 



0,4  CaO,  0.6  Pb0  1 

55 

0.2  CaO,  O.S  PbO  ! 

56 — 

1 .0  PbO  1 

II 

RESULTS 

OF  GLOST  BURN— VARIATIONS  IN  RO  MEMBERS  - Cone  1. j 

Glaze 

Cone 

Description  of  ^laze 

1 

1 

Purple  red  with  good  aventurine  crystals,  glossy. 

2 

1 

Black,  good  aventurine  crystals,  glossy.  i 

3 

1 

Deep  brown,  good  crystallization,  matt  textiors. 

4 

1 

Purple-brown,  no  crystals,  glossy. 

5 

1 

Reddish-black,  good  crystallization,  matt  texture! 

6 

1 

Black,  metallic  separations,  glossy. 

7 

1 

Red-purple , no  crystals,  glossy. 

g 

1 

Purple,  no  crystals,  semi-matt  texture. 

9 

1 

Brown-purple,  no  crystals,  glossy. 

10 

1 

n 

11 

2 

Black,  metallic  and  aventurine  separations , glossy  1 

12 

1 

Red-brown,  minute  aventurine  crystals,  glossy. 

13 

1 

Brown-purple,  no  crystals,  glossy. 

14 

1 

Purple,  no  ccystals,  glossy. 

15 

1 

Red,  no  crystals,  glossy. 

i 16 

1 

Red,  no  crystals,  glossy. 

17 

1 

Red-purple,  no  crystals,  glossy. 

IS 

1 

19 

1 

Red-purple,  few  minute  crystals,  glossy. 

20 

1 

Red,  no  crystals,  glossy. 

21 

1 

Red-gold,  good  aventurine,  semi-matt. 

i 

'■I  ■■t 


I 

/ 


1 


j: 


V 


t 


r 

t. 


i 


-32- 


Glaze 

22 

23 

24 

25 

26 

27 

2S 

29 

30 

31 

32 

33 
3^ 

35 

36 

37 
3S 

39 

40 

41 

42 

^3 

44 

^5 

46 

47 

45 


Cone 

1 

1 

1 

1 

1 

1 

1 

1 

1 

1 

1 

1 

1 

1 

1 

1 

1 

01 

2 

1 

1 

1 

1 

1 

1 

1 

1 


Description  of  glaze 
Deep  purple,  good  aventurine,  glossy. 
Red-purple,  no  crystals,  glossy. 

Deep  brown-purple , few  crystals,  glossy. 

Deep  gray-purple,  few  crystals,  glossy. 
Red“purple,  no  crystals,  glossy. 

Deep  gray-purple,  very  minute  crystals,  glossy. 

" , no  crystals,  glossy, 

n tt  ti 

» f * 


Red-purple,  no  crystals,  glossy. 

Dull  black,  very  few  crystals,  dull. 

Deep  purple,  very  minute  crystals,  glossy. 

« « It 

» » • 

Red-purple,  no  crystals,  glossy. 

Red-purple,  no  crystals,  glossy. 

Deep  brown,  metallic  and  aventurine  separations 
glossy . 

Gold-jpnrple , very  minute  crystals,  glossy. 
Red-purple,  no  crystals,  glossy. 

Red-brown,  no  crystals,  matt  texture. 

Black,  no  crystals,  matt-texture. 

Deep  brown,  no  crystals,  semi-matt  texture. 

Deep  brown-purple,  no  crystals. 

Red-brown,  no  crystals,  glossy. 

n n n 

> » • 

Red,  no  crystals,  glossy. 

Black-purple,  no  crystals,  semi-glossy. 

n « « 

» t • 


» 


. , , ,f  '• ; tytr'  • • , . ■.  ,:  ■ 

V 

/r 


I 


1 


t 


n 

')i 


\ 


? 


ri 


-33- 


Glaze 

Cone 

Description  of  glaze 

^9 

1 

Black-purple,  no  crystals,  semi-glossy. 

50 

1 

Deep  brown,  no  crystals,  semi-glossy. 

51 

2: 

Black,  no  crystals,  dull,  under-fired. 

52 

2 

Brown,  " » ^ * 

53 

1 

Red-brown,  no  crystals,  dull , under -fired. 

5|f 

1 

« « n tt  . 

» » » • 

55 

1 

Red,  no  crystals,  matt  texture. 

56 

1 

H ^ If  It  ^ 

■.» » > * 

DisGUSBion  of  Results  of  Gloat  Burn  with  Variable  R 0 
Soda  seems  to  be  the  member  of  the  R 0 group  which  most  assists 
crystallization.  The  glazes  centered  around  the  soda  vertex  of  the 
pyramid  all  showed  crystallization  to  a marked  extent  but  the  amount 
of  crystallization  diminished  toward  the  other  vertices.  Potash 
was  the  next  agent  most  conducive  to  crystallization,  which  is  in- 
dicated by  the  formation  of  crystals  in  the  trials  all  the  way  from 
the  soda  to  the  potash  vertex.  Lime  and  lead  both  seem  to  hinder 
the  formation  of  crystals,  probably  because  of  the  high  viscocity 
of  the  glazes  containing  these  R 0 members. 

Lead  and  lime  both  made  the  glazes  more  refractory  so  that 
their  maturing  temperature  is  well  above  cone  1.  Lime  made  the 
most  refractory  glaze  of  all. 

The  only  effects  noticed  on  the  color  was  that  lead  gave  the 
glazes  a reddish-purple  tinge  which  became  more  pronounced  as  the 
lead  vertex  was  approached,  becoming  quite  red-purple  at  the  lead 
vertex , 


-34- 

Conclusions  on  the  Effect  of  Soda,  Lime,  Potash  and 
Lead  on  Aventurine  Glazes, 

From  the  above  work,  the  follov/ing  conclusions  are  deduced: 

1,  Soda  aids  the  production  of  aventurine  glazes  more  than 
any  of  the  other  R 0 member®  employed, 

2,  Lime  gives  the  most  refractory  glaze  of  all  R 0 members 
employed, 

3,  Potash  is  the  second  best  agent  in  the  production  of  Aven- 
turine glazes  and  lead  is  next, 

4,  The  color  of  the  glazes  is  little  effected  by  the  R 0 
members  employed  except  by  lead  which  gives  a decided  red- 
purple  color  to  the  glazes, 

5»  The  influence  of  soda  in  the  production  of  aventurine 
glazes  in  combination  with  other  R 0 oxides  is  very  strong, 

A little  soda  in  the  glaze  makes  a vast  difference  in  the 
fusibility  and  the  tendency  to  form  crystals. 

XI 

General  Conclusions, 

The  general  conclusions  drawn  from  this  study  of  aventurine 
glazes  are;- 

lo  For  the  production  of  aventurine  glazes  a slowly  increas- 
ing and  steadily  oxidizing  fire  is  necessary.  The  rate  of 
cooling  must  be  slow  for  the  proper  production  of  aventurine 
crystals . 

2,  An  increase  in  SiOg  requires  an  increase  FegO^  to  produce 
aventurine  glazes,  (Schurect) 

3*  An  increase  in  the  iron  contentincreases  the  size  and 


t t.A-  »'i-.l'OJ>  %o 

* L:.  .J ■ • A 4t  V.'  tH  L i 

"•  ‘ '>.  vilTCO  -^.CL  ''i  e\-i^  ^ -r:  w •-..■■ 

;.  l;  jc  i a tt  it^,.  ' 

0 a 'itrivo  t;'..'. 

.Li.-,  iv  Il-Jsl  ' ’ C €»^  1 


- ' V 


■•'  . 1 -''u;:  ■ 


t ^'j2  c©"  -'o  f. 

r^A‘’ 

- . L-  f 1 : i,  ft 


V' 

PV 

ci  V is: 

V.  u S 

»V  1 


'tv 


\ii' 


'^'i.;Cv  J*;-;  U»'J  .*4  'S- 1 ^ iP 

nvi-** '^y:r  V ■■■^  -.r.'-i  :.i  " R 'i'-f!:'  rf*t^  ,i  :J :f^!ifi.nvco  .'^  i .'i?^-A'; 

r'.r'.5r'3s‘f.  1 : rd.«V  ; «•  5 \ 4tf,  v:i  .i  •-•]::';MX 

• V 1 

. *.  ■ K •■  I"  :1p'i  C.J  V-f;2rl'^'  ' V .' i £,H  L c:  A 


'A>;:  ■ 


V 


v ♦ 


I v'; 


\ 

) V» 


number  of  crystals  and  also  the  refractoriness  of  the  gla^^e. 

(Schurecht) 

4.  An  increase  of  Na^O  increases  crystallization.  Bromberg 
incorporated  this  conclusion  in  his  v/oric.  (See  page  7 of 
this  thesis).  The  conclusion  was  verified  in  my  own  worJic  on 
variations  in  the  RO  components. 

3.  Aventurine  glazes  may  be  formed  in  the  presence  of  .2  mole  of 
Al^O^.  (Bromberg,  see  page  7 of  this  thesis) 

6.  Aventurine  crystals  may  be  formed  in  the  presence  of  CaO  even 
v>rhen  there  is  as  much  as  .4  mole  present . (Bromberg,  see  page  7 
of  this  thesis) 

7.  Decreasing  the  lead  increases  crystallization  and  decreases‘ the 
gloss.  (Bromberg,  see  page  7 of  this  thesis)  iviy  work  on  vari- 
ations in  the  RO  members  verified  his  statement, 

8.  Aventurine  glazes  are  notrestricted  to  any  pa-rticular  molecular 
or  oxygen  ratio,  but  come  within  the  limits  of  good  glazes. 
(Bromberg,  see  page  7 of  this  thesis) 

9.  A low  iron  oxide  content  (0.73  moles)  together  v/ith  a low 
boric  acid  content  (1.23  naoles.)  with  high  alumina  (Q.I3  moles) 
and  silica  (7*00  moles)  content  produces  the  best  goldstone 
effects.  This  is  my  own  observation  and  agrees  with  the  obser- 
vation of  Schurecht. 

10.  Crazing  occurs  least  in  the  areas  of  best  crystallization. 

This  is  contrary  to  the  behavior  of  most  crystalline  glazes 
but  seems  consistently  true  with  aventurine s, 

1 1 . From  the  observations  of  Bromberg  and  from  the  conclusions 

of  my  own  work  on  the  variations  in  the  RO  contents,  the  order 
of  beneficial  effect  upon  crystallization  of  the  RO  members 
studied  is  as  follows:  1.  soda.  2.  Potash,  3,  Lead,  4,  Lime, 


* K 


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■ ' ‘ ’ ' • - V-  ■ - - ' :' ' ' V.' 

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■*•  - ■•  ft'  . . , y.'i  ,,  , i.,Ji|i'^ 


4Af<  ai  (Si?ili'ife.ir  D4IA*  isjlf  wfoij]pv  «;.4I.;;;,(;6Jbi<j^' ,. 

^ ' ktii  ^ ' '.  - .;  *?■  's,  . ■.■'^:v;' 

, .,  V . Cfk,  »4t 

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(fiipsfw  311:;  va^«ia3S'j%.0t.^ 

iibvo  (JiO  Uo  s^itto » a'i'ij  6f;i  rJ 'f  s«nol  e0''’^fc 

»■-.■■  " , ,.  i .-  ■ • ■uT'Nii*,*' 


i. ., 

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Is  k.  “■  fj-j  1^  AK*  ' " ? ’>  1 »f  * ^ 

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UH  ,Oi^£^ 


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Ar  * io  aa»l«  swJ  aX 
e’e  tfixiU-ij  .1  ■.  eo« • wit ' fciU  bi^;t-t.a-'j4!^K)i'  '•  ‘^' 

1 -.,  - • J--  •-  *'  W 


( 


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; ;it«a  L£U^ia^1h  r.’*  f *-.  m;  «V';Sto.-r 


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■v-<  . M ■'  - Wi*  »if  • . . ...U/'  '■  V'  ' .4^' '..  “ 


-36- 

In  concluding  this  thesis  1 wish  to  express  my  thanks  to 
Professor  C.  W.  Parmelee  of  the  Ceramic  hngineeriQgdepartment  of 
the  University  of  Illinois  f orchis  aid^in  directing  my*  work  and 
his  assistance  in  tne  collection  of  material,  I further  wish  to 
acknowlege  my  indebtedness  to  IJethan  Bromberg  and  H.  G,  Schorecht 
for  the  valuable  information  they  have  produced  in  their  wrrx  on 
the  subject  of  aventurine  glazes,  I also  wish  to  thanx  the  Ceramic 
Engineering  students  of  the  class  of  1^22  for  the  information 
they  have  given  to  me  through  their  study  of  aventurine  glazes 
and  the  report  of  their  work  which  I was  allowed  to  summarize. 


